Method for fabricating a flexible electronic structure and a flexible electronic structure

Abstract

Flexible electronic structure and methods for fabricating flexible electronic structures are provided. An example method includes applying a first layer to a substrate, creating a plurality of vias through the first layer to the substrate, and applying a second polymer layer to the first layer such that the second polymer forms anchors contacting at least a portion of the substrate. At least one electronic device layer is disposed on a portion of the second polymer layer. At least one trench is formed through the second polymer layer to expose at least a portion of the first layer. At least a portion of the first layer is removed by exposing the structure to a selective etchant to providing a flexible electronic structure that is in contact with the substrate. The electronic structure can be released from the substrate.

The invention claimed is: 
     
       1. A method for fabricating a flexible electronic structure, said method comprising:
 applying a first layer to a portion of a substrate; 
 removing selected portions of the first layer to provide a plurality of vias, wherein a portion of the vias extend substantially to a surface of the substrate; 
 disposing a second polymer layer, such that portions of the second polymer layer conform to a dimension of at least one of the plurality of vias and forms a plurality of anchors that contact at least a portion of the substrate, wherein the second polymer layer is more resistant to a selective etchant than the first layer; 
 disposing at least one electronic device layer above a portion of the first layer and/or the second polymer layer; 
 applying an adhesive layer to a portion of the second polymer layer prior to disposing the at least one electronic device layer; 
 forming at least one trench through the second polymer layer and the at least one electronic device layer to expose at least a portion of the first layer; 
 exposing at least a portion of the first layer to the selective etchant through the at least one trench; and 
 removing, by the selective etchant, portions of the first layer, thereby providing the flexible electronic structure, wherein at least one anchor of the plurality of anchors remains in contact with at least a portion of the substrate. 
 
     
     
       2. The method of  claim 1 , wherein an average width of the vias is selected such that at least some of the plurality of anchors resist the selective etchant to remain substantially in contact with at least a portion of the substrate. 
     
     
       3. The method of  claim 1 , further comprising:
 applying a removable medium to a portion of the at least one electronic device layer; and 
 applying a force to separate the flexible electronic structure from the substrate; 
 wherein the removable medium is selected such that the adhesion strength of the removable medium to the at least one electronic device layer is greater than the adhesion strength of the anchors to the substrate. 
 
     
     
       4. The method of  claim 1 , wherein an average width of the plurality of anchors is in a range from about 10 μm to about 50 μm. 
     
     
       5. The method of  claim 1 , wherein an average width of the plurality of anchors is in a range from about 0.1 μm to about 1000 μm. 
     
     
       6. The method of  claim 1 , wherein at least some of the plurality of anchors have a substantially circular cross-section. 
     
     
       7. The method of  claim 1 , wherein at least some of the plurality of anchors have a substantially hexagonal cross-section, a substantially oval cross-section, a substantially rectangular cross-section, a polygonal cross-section, or a non-polygonal cross-section. 
     
     
       8. The method of  claim 1 , wherein the plurality of anchors are formed in a two-dimensional array. 
     
     
       9. The method of  claim 1 , wherein an average width of each of the plurality of vias is in a range from about 10 μm to about 50 μm. 
     
     
       10. The method of  claim 1 , wherein an average width of each of the plurality of vias is in a range from about 0.1 μm to about 1000 μm. 
     
     
       11. The method of  claim 1 , wherein respective ones of the plurality of vias are spaced apart by an average separation ranging from about 50 μm to about 1,000 μm. 
     
     
       12. The method of  claim 1 , wherein respective ones of the plurality of vias are spaced apart by an average separation ranging from about 0.2 μm to about 10,000 μm. 
     
     
       13. The method of  claim 1 , wherein respective ones of the plurality of vias are spaced apart by an average separation ranging from about 200 μm to about 800 μm. 
     
     
       14. The method of  claim 1 , wherein the first layer comprises polymethylmethacrylate, silicon dioxide, chromium, or titanium. 
     
     
       15. The method of  claim 1 , wherein the second polymer layer comprises polyimide, polyethylene naphthalate, polybenzobisoxazole, benzocyclobutene, siloxane, or a liquid crystal polymer. 
     
     
       16. The method of  claim 1 , wherein the first layer comprises polymethylmethacrylate and the selective etchant comprises acetone. 
     
     
       17. The method of  claim 1 , wherein the first layer comprises silicon dioxide and the selective etchant comprises hydroflouric acid. 
     
     
       18. The method of  claim 1 , wherein the first layer comprises chromium and the selective etchant comprises cerric ammonium nitrate. 
     
     
       19. The method of  claim 1 , wherein the first layer comprises titanium and the selective etchant comprises hydroflouric acid or hydrochloric acid. 
     
     
       20. The method of  claim 1 , wherein the substrate comprises at least one of a test structure, a manufacturing alignment structure, a piezoelectric structure, and a lithography alignment mark. 
     
     
       21. The method of  claim 1 , wherein the adhesive is a polyimide or other polymer. 
     
     
       22. The method of  claim 1 , further comprising curing the adhesive layer prior to disposing the at least one electronic device layer. 
     
     
       23. The method of  claim 1 , wherein the at least one electronic device layer comprises at least one of a metal, a semiconductor, and a dielectric. 
     
     
       24. The method of  claim 1 , further comprising curing the first layer at a cure temperature of the second polymer layer prior to applying the second polymer layer, wherein the cure temperature of the second polymer layer is higher than a cure temperature of the first layer. 
     
     
       25. The method of  claim 1 , further comprising patterning a mask on the at least one electronic device layer prior to forming the at least one trench, wherein the mask forms a pattern of the at least one trench. 
     
     
       26. The method of  claim 1 , further comprising removing selected portions of the first layer using an oxygen plasma etch. 
     
     
       27. The method of  claim 1 , wherein the at least one trench is formed by using lithography and etching, using laser ablation, by mechanical cutting or using pure photopatterning. 
     
     
       28. The method of  claim 1 , further comprising:
 applying a third polymer layer to at least a portion of the at least one electronic device layer; and 
 forming the at least one trench through the third polymer layer, the second polymer layer, and the at least one electronic device layer to expose at least a portion of the first layer. 
 
     
     
       29. The method of  claim 28 , wherein the third polymer layer is applied using a spin coating process, spray coating, lamination, casting, or vapor deposition. 
     
     
       30. The method of  claim 28 , wherein a thickness of the third polymer layer is configured such that the at least one electronic device layer is at a neutral mechanical plane of the electronic structure. 
     
     
       31. The method of  claim 1 , further comprising:
 applying a removable medium to a portion of the at least one electronic device layer; and 
 applying a force to separate the flexible electronic structure from the substrate. 
 
     
     
       32. The method of  claim 31 , further comprising removing the removable medium using selective removal process. 
     
     
       33. The method of  claim 32 , wherein the selective removal process is exposure to a solvent, heating, exposure to UV light, or an oxygen plasma etch. 
     
     
       34. The method of  claim 1 , wherein the substrate is a rigid substrate. 
     
     
       35. The method of  claim 1 , wherein the substrate has a higher Young's modulus than the second polymer layer. 
     
     
       36. A flexible electronic structure comprising:
 a second polymer layer having a first surface and a second surface, wherein the first surface comprises a plurality of anchors; and 
 at least one electronic device layer disposed above the second surface of the second polymer layer, 
 wherein the electronic structure is fabricated according to the method of  claim 1 . 
 
     
     
       37. A method for fabricating a flexible electronic structure, said method comprising:
 applying a first layer to a portion of a substrate; 
 removing selected portions of the first layer to provide a plurality of vias, wherein a portion of the vias extend substantially to a surface of the substrate; 
 disposing a second polymer layer, such that portions of the second polymer layer conform to a dimension of a number of the vias and forms anchors that contact at least a portion of the substrate, wherein the second polymer layer is more resistant to a selective etchant than the first layer; 
 disposing at least one electronic device layer above a portion of the first layer and/or the second polymer layer; 
 applying an adhesive layer to a portion of the second polymer layer prior to disposing the at least one electronic device layer; 
 forming at least one trench through the second polymer layer and the at least one electronic device layer to expose at least a portion of the first layer; and 
 exposing at least a portion of the first layer to the selective etchant through the at least one trench to remove portions of the first layer, thereby providing the flexible electronic structure, wherein at least one anchor of the flexible electronic structures contact the substrate; and 
 separating the flexible electronic structure from the substrate. 
 
     
     
       38. The method of  claim 37 , wherein separating the flexible electronic structure from the substrate comprises:
 applying a removable medium on a portion of the at least one electronic device layer; and 
 applying a force to the removable medium to separate the anchors from the substrate. 
 
     
     
       39. The method of  claim 38 , wherein the removable medium is selected such that the adhesion strength of the removable medium to the at least one electronic device layer is greater than the adhesion strength of the anchors to the substrate. 
     
     
       40. The method of  claim 39 , further comprising removing the removable medium by exposure to a solvent, heating, exposure to UV light, or using an oxygen plasma etch. 
     
     
       41. The method of  claim 40 , wherein the removable medium is removed by exposure to water. 
     
     
       42. The method of  claim 38 , further comprising exposing the flexible electronic structure on the removable medium to an oxygen plasma, wherein the oxygen plasma removes a portion of the removable medium that is not adhered to the flexible electronic structure. 
     
     
       43. The method of  claim 38 , further comprising depositing at least one additional electronic device layer on portions of the second polymer layer. 
     
     
       44. The method of  claim 38 , further comprising exposing the second polymer layer of the flexible electronic structure to an oxygen plasma to create a highly oxygen-terminated surface; and adhering a second substrate to the highly oxygen-terminated surface of the flexible electronic structure. 
     
     
       45. The method of  claim 44 , further comprising exposing the second substrate to an oxygen plasma to create a highly oxygen-terminated surface; and adhering the highly oxygen-terminated surface of the second substrate to the highly oxygen-terminated surface of the flexible electronic structure. 
     
     
       46. The method of  claim 44 , wherein the second substrate comprises at least one of a flexible material and a stretchable material. 
     
     
       47. The method of  claim 44 , wherein the second substrate comprises an elastomeric material, a rubber material, a plastic material, or a fabric. 
     
     
       48. The method of  claim 44 , wherein the second substrate comprises a silicone-based material. 
     
     
       49. The method of  claim 37 , wherein the substrate is a rigid substrate. 
     
     
       50. The method of  claim 37 , wherein the substrate has a higher Young's modulus than the second polymer layer. 
     
     
       51. The method of  claim 37 , further comprising:
 applying a third polymer layer to at least a portion of the at least one electronic device layer; and 
 forming the at least one trench through the third polymer layer, the second polymer layer, and the at least one electronic device layer to expose at least a portion of the first layer. 
 
     
     
       52. The method of  claim 51 , wherein the third polymer layer is applied through a spin coating process, spray coating, lamination, casting, or vapor deposition. 
     
     
       53. The method of  claim 51 , wherein a thickness of the third polymer layer is configured such that the at least one electronic device layer is at a neutral mechanical plane of the electronic structure. 
     
     
       54. A flexible electronic structure comprising:
 a second polymer layer having a first surface and a second surface, wherein the first surface comprises a plurality of anchors; and 
 at least one electronic device layer disposed above the second surface of the second polymer layer, 
 wherein the electronic structure is fabricated according to the method of  claim 37 .